2. Relevance of law and equity.

The effect of mistake differed originally as between common law and equity1. The difference is still of more than historical importance, despite fusion of the two systems2. The legal rules still apply to claims for the recovery of money paid under a mistake3, or of property purportedly transferred under a mistake4, and to cases where a party to a claim on a contract or specialty5 is entitled to the plea non est factum6, or where the case of one of the parties to a claim founded on contract is that there was no contract between them